1. Field of the Invention
The present invention relates generally to dimension measuring systems and more particularly to a dimensioning system utilizing one or more spinning scanning drums having light transmitting holes extending therethrough to provide fast and accurate volume measurements even under adverse operating conditions.
2. Description of the Related Art
Systems for determining the three dimensional measurements of objects are well known. Typically, such devices transmit beams of light across a conveyor in the path of the object to be measured. If width and height are to be measured, a frame is positioned around the conveyor with the vertical frame members transmitting and receiving beams for determining the height of the object, and the horizontal frame members transmitting and receiving beams for determining the width of the object. Still further means may be used for determining the length of the box. If the object is oriented at an angle relative to the conveyor, an algorithm may be employed for determining the actual volume of the box.
U.S. Pat. No. 4,773,029 discloses one such method for determining the three dimensional measurements of objects passing on a conveyor. A frame is placed around the conveyor, the frame having two transmitter sides and two receiver sides, with the transmitters opposed from the receivers. Each transmitter side comprises an array of light emitting diodes, and each receiver side comprises a light receiver for each LED. The method includes a signal processing algorithm to insure that light between a single light emitter and single light receiver is unambiguously received.
Another device for measuring the dimensions of an object is shown in U.S. Pat. No. 4,192,613. This device also comprises opposed transmitting and receiving frame members wherein the transmitting frame member comprises a plurality of closely spaced LED light transmitters, and the receiver comprises a light detector for each transmitted light beam. Other devices which employ opposed light transmitters and light receivers wherein each light receiver has a corresponding light transmitter are shown in U.S. Pat. Nos. 5,130,532; 5,198,661; and 5,243,183.
An inherent limitation in such devices is that the maximum resolution achievable is determined by the density of light transmitters on the light transmitting side of the measuring apparatus, and the density of the light receivers which may be placed on the receiving end of the measuring apparatus. For example, in order to register measurements on the order of 0.1 inches, the light transmitters and the light receivers must be very densely packed. This is not only difficult from a manufacturing standpoint, but it is expensive. Also, detection and replacement of defective transmitting and receiving elements is difficult. Accordingly, it would be desirable to have an apparatus which could accurately measure the dimensions of an object passing on a conveyor, without the need for densely packed transmitter and receiver units.
Another device for measuring the dimensions of an object is shown in U.S. Pat. No. 3,943,361. This device includes a rotating drum which having reflectors arranged in a spiral path along the surface of the drum. A light source is aimed at the reflectors, which are angled so that as the drum rotates a scanning light beam is directed across a conveyor. A photo-detector is aimed at the conveyor and registers light as it is reflected from an object passing on the conveyor. Because the measurement of the dimensions of the box are based upon reflection, boxes which are angled relative to the conveyor may be inaccurately measured, and the reflectivity of the box and/or background lighting may lead to errors as well.